The present invention relates to a solid acid-base catalyst, which is suitably provided for various reactions, such as syntheses of an olefin (alkene) or an ether through a dehydration reaction of an alcohol, syntheses of an aldehyde or a ketone through a dehydrogenation reaction of an alcohol, hydration and isomerization reactions of olefin, alkylation, esterification, amidation, acetalization, amination, hydrogen shift reactions, aldol condensation reactions and polymerization reactions.
Conventionally, many processes using a solid acid catalyst or a solid base catalyst, such as dehydration reactions of alcohols, hydrations and isomerization reactions of olefins, alkylation reactions, esterification reactions and aldol condensation reactions, and polymerization reactions have been studied.
As such a solid acid-base catalyst, a solid acid catalyst, such as zeolite, silica-alumina and titania-silica, and a solid base catalyst, such as magnesium oxide and calcium oxide are known.
However, the above conventional solid acid catalyst and the solid base catalyst have disadvantages that strict reaction conditions such as high temperature and high pressure, etc. are required.
In addition, the above conventional solid acid catalyst also has a disadvantage that its activity is decreased due to deactivation caused by carbon deposition at the time of reaction.
Therefore, it is desired to obtain a solid acid catalyst and a solid base catalyst, which are capable of being prepared easily with excellent reproducibility and of displaying catalytic activity under mild reaction conditions, without deactivation, as well as solid acid-base cooperative catalyst which has both an acid point and a base point, that is peculiar to a solid catalyst, and highly selectively produces reactions through a concerted action of both active points (hereinafter, these catalysts are referred to as solid acid-base catalysts).
The present invention was invented based upon the above conventional problems, and it is an object of the present invention to provide to provide a new solid acid-base catalyst, which is capable of being prepared easily with excellent reproducibility and is capable of displaying catalytic activity under mild reaction conditions and whose activity is hard to be lowered due to deactivation.
After the provision of a new solid-acid-base catalyst which achieves the above object was studied, we found that a solid acid-base catalyst containing vanadium pentoxide hydrate sufficiently displays catalytic activity under mild conditions for various reactions, such as the syntheses of olefins or ethers through dehydration reactions of alcohols, syntheses of aldehydes or ketones through dehydrogenation reactions of alcohols, hydration and isomerization reactions of olefins, alkylations, esterifications, amidations, acetalizations, aminations, hydrogen shift reactions, aldol condensation reactions and polymerization reactions. Then, the present invention was completed.
In other words, in order to achieve the above object, the solid acid-base catalyst of the present invention is characterized by containing vanadium pentoxide hydrate. In addition, in the above solid acid-base catalyst, it is desirable that the vanadium pentoxide hydrate has a composition which is represented by the following general formula (1):
V2O5xc2x7nH2Oxe2x80x83xe2x80x83(1)
where n is 0.1-3.
In accordance with the above arrangement, the solid acid-base catalyst can display catalytic activity under mild conditions for various reactions, such as syntheses of olefins or ethers through dehydration reactions of alcohols, syntheses of aldehydes or ketones through dehydrogenation reactions of alcohols, hydrations and isomerization reactions of olefins, alkylations, esterifications, amidations, acetalizations, aminations, hydrogen shift reactions, aldol condensation reactions, and polymerization reactions.
Furthermore, in the above solid acid-base catalyst, it is desirable that the vanadium pentoxide hydrate has a layered structure and is obtained by intercalating at least one kind of substance, which is selected from a group composed of metallic ions, ammonium ions and metal complexes. Moreover, it is desirable that the vanadium pentoxide hydrate has a layered structure and is obtained by intercalating an organic substance between layers. Further, it is desirable that the organic substance is a compound containing nitrogen.
As a result, since the catalytic activity can be further improved by adjusting the acid-base properties of the solid acid-base catalyst, more remarkable catalytic activity can be displayed under mild reaction conditions. Therefore, the solid acid-base catalyst can be suitably applied to various reactions, such as syntheses of olefins or ethers through dehydration reactions of alcohols, syntheses of aldehydes or ketones through dehydrogenation reactions of alcohols, hydrations and isomerization reactions of olefins, alkylations, esterifications, amidations, acetalizations, aminations, hydrogen shift reactions, aldol condensation reactions, and polymerization reactions.
Furthermore, in the solid acid-base catalyst, it is most preferable that the vanadium pentoxide hydrate is obtained such that after ion exchange of a vanadate aqueous solution is made by using a proton-type cation exchange resin, the ion-exchanged solution is polycondensed and is dried. Moreover, it is secondarily preferable that the vanadium pentoxide hydrate is arranged by adding mineral acid to a vanadate aqueous solution or by hydrolyzing vanadyl alkoxide.
As a result, since the solid acid-base catalyst has excellent properties and the catalytic activity can be further improved, a more remarkable catalytic activity can be displayed under mild reaction conditions. Therefore, the solid acid-base catalyst can be suitably applied to various reactions, such as syntheses of olefins or ethers through dehydration reactions of alcohols, syntheses of aldehydes or ketones through dehydrogenation reactions of alcohols, hydrations and isomerization reactions of olefins, alkylations, esterifications, amidations, acetalizations, aminations, hydrogen shift reactions, aldol condensation reactions, and polymerization reactions.
For a fuller understanding of the nature and advantages of the invention, reference should be made to the ensuing detailed description taken in conjunction with the accompanying drawings.